FM receivers that use CTCSS typically have a low pass filter (~250
Hz) that directs the CTCSS to the CTCSS deocder, and a high pass
filter that blocks the CTCSS from the normal audio chain. FM squelch
circuits use another high pass filter (4K or so) that is used to
determine the quieting on a channel.
73,
Mark N5RFX
At 11:47 AM 8/17/2008, Scott Miller wrote:
>I'm afraid I don't even know how the radio
>suppresses the PL tone - 100 hz is most certainly within the audible
>range. Is everything filtered below a certain cutoff frequency, and if
>so, what's the cutoff?